The true northerner. [volume] (Paw Paw, Mich.) 1855-1920, 1887-08-31
MECHANICAL.

A GLASGOW engineering firm has
constructed what is said to be the
largest planning machine in the world,
specially intended and designed to be
employed in connection with the
preparation of steel plates for the
Orders of railway bridge in New
South Wales. The weight of this vast
machine is stated to be some thirty-five
tons, and it is capable of planning the
edge of q plate thirty eight feet in
length by five feet wide.
The largest dam in the world is to
be built across the upper end of the San
Mateo Cany on, about four miles west of
the village of San Mateo. The dam
will consist of solid wall of concrete
from hillside to hillside. 1t will be 700
feet long, 10 feet high. 175 feet thick
ut the base and twenty feet thick at the
top. The reservoir which will be
formed by this dam will have capacity
of $4,000, 900 gallons, and some time
in the future will be connected with
the San Francisco watershed by tun-
mel five miles long.
To BUILD q chimney that will draw
forever and not fill up with SCOT, you
must build it large enough, sixteen
inches square; use good brick, and clay
instead of lime up to the comb; plaster
it inside with clay mixed with salt; for
chimney tops use the very best of
brick, wet them and lay them in ce-
ment mortar. The chimney should not
be built tight to beams and rafters !;
there is where the crack in your chin
neys comes, and where most of the fires
originate, as the chimney sometimes
gets red hot. A chimney built
from cellar up is better and less dan
gerous than one hung on the wall.
Don't get your stovepipe hole too close
to the ceiling, eighteen inches from it.
To MARK off the division in the cir
cles of most elaborate instruments of
precision by hand is task requiring
immense skill and exquisite accuracy
as each one of the divisions must be
identical in shape and size with all the
rest, each circle divided into $50 de-
grees, each degree into sixty minutes,
and each minute into sixty seconds,
equal to 100, 900 seconds in each circle !;
while delicate astronomical and some
other instruments must have their cir
cles divided into divisions much small
er than this. Copying machines have
been useful in this work by means Of q
microscope, the lines indicated by the
machine being gone over to engrave
them deep enough; but such hand la
Dor is not only excessively arduous and
fatiguing, but requires a great deal Of
time, some thirty-six hours being re-
CURED to divide two-minute arc in
this way. To obviate this difficulty of
time and labor, machine has been
contrived, which is pronounced pecul-
lar success, its accuracy being marvel
Gus. This apparatus is set in motion
by a small turbine, and works on
calmly and evenly until the last stroke
is cut, performing In few hours what
it takes a man many days to accom-
plish, and with practically perfect ac-
curacy.
A WRITER in recent number of the
Rcr1Je ChrOnOmetrique states that
holes may be bored through glass by
means of a rapidly rotating steel borer
kept moist with turpentine previously
mixed with oXalic acid or the juice OF
onions. A writer in the ZitSchrift
| HlStTunlt 7lte1lkl9de quite properly
ueCldIeS THESE IdSI- Hulntu duulIlOuo W
be immaterial. He adds: "The object
may be accomplished readily by using
a borer tempered at as low tempera-
ture as possible $50 as to be as hard as
glass, aud rotating it only slowly,
taking particular care that it is kept
constantly moist with turpentine. Glass
may a so be bored quite readily with
the aid of petroleum, though this does
not possess the power of cooling the
tool in the same degree as the oil of
turpentine. In order to prevent the
chipping of edges at the commence
ment of boring, it is preferable to make
a preliminary hole with glass-hard,
three-cornered steel point This hole
should lie a trifie larger than that
which is to be bored through the glass.
The latter may then be drilled as de-
scribed before. IN order to prevent
the glass at the opposite side from
breaking or chipping when the borer
begins to pass through piece of glass
must be cemented against the other
side"